The present invention is directed to a solution formed by mixing a silicate solvent and a photocurable arylsiloxane material dissolved therein which can be used, as a spin-on-solution, for example, to form striation-free films having good reflectivity characteristics. Photocurable arylsiloxane materials, suitable for use as interlayer dielectric films, which can be spin coated are known to persons of ordinary skill in the art. For example, U.S. Pat. No. 4,349,609 to S. Takeda et al. mentions the use of a variety of organic solvents for such arylsiloxane materials, including a mixture of cyclohexanone and toluene, a mixture of n-butyl cellosolve acetate and toluene, a mixture of isophorone and toluene, metacresol, and a mixture of N-methyl-2 pyrrolidone and N,N-dimethylacetamide. Various of these enumerated solvents are either corrosive, are teratogenic, are carcinogenic, or are irritants. More recent U.S. Pat. No. 4,600,685 to T. Kitakohji et al. also indicates the spin-coating of organosiloxane resins to form interlayer dielectric films. This reference mentions such organic solvents as toluene, cyclohexane, methyl cellosolve acetate (a suspected teratogen), alcohols, and ketones. Example 4 illustrates a mixed solvent of monobutylcellosolve acetate and toluene.
Another example of a recent U.S. patent which describes the spin-coating of arylsiloxane oligomers and polymers dissolved in organic solvents to form interlayer dielectric films is U.S. Pat. No. 4,663,414 to W. E. Estes et al. which indicates the use of xylene as a preferred aromatic hydrocarbon as the solvent. This patent indicates that toluene and benzyl alcohol are less preferred solvents for use in the spin-coating procedure.
More recently, in U.S. Ser. No. 342,150, filed Apr. 24, 1989, blends of alkoxyalkanol solvents and photocurable arylsiloxane materials have been described.
All of the approaches previously mentioned rely upon the use of a relatively volatile organic solvent to dissolve the arylsiloxane material. The use of such a relatively volatile solvent component has certain shortcomings including: the production of formulations which have a lower degree of viscosity than desired due to the need to have enough solvent present to maintain spinability for the liquid formulation; the possible production of pinholes in the film that is produced due to the evaporation of residual organic solvent; and the problems associated with human exposure to the volatile organic solvent during the process of film formation.
It is known to use ethyl silicate as a solvent with a narrowly defined hydrophobic organosilicon "fluid" which is described as containing silica, tetraethoxysilane and oligomers formed as a result of partial hydrolytic polycondensation of the latter (see U.S.S.R. Patent No. 1,156,857). The resulting composition is indicated as being useful in coating a porous article with the ethyl silicate being identified as guaranteeing a more complete filing of the pores of the article. This reference does not suggest that solid siloxane materials can be dissolved in ethyl silicate nor does it suggest selection of a photocurable arylsiloxane oligomer or polymer as the organosilicon component.